There is a need for couplings to communicate hydraulic fluid to and from tractor mounted hydraulic power sources. There is also a need to communicate hydraulic fluid to and from agricultural or construction implements. A directional valve downstream from the power source controls the direction of the fluid in the hydraulic lines and, hence, the direction of the implement. Interposed between the directional valve and the load are a manifold and shut off valves. Typically, female coupling halves are carried in the manifold and male coupling halves are affixed to hydraulic lines leading to and from the implement. Use of a manifold is optional and female coupling halves may be mounted directly on the tractor or other device. It is therefore necessary to provide a coupling having valves which remain open and stable as the flow direction is reversed and which will not result in the valves closing upon reversal of flow and unintentionally and undesirably preventing flow (i.e., flow checking).
When an implement is disconnected (uncoupled) from the manifold, it is desirable to maintain implement in a safe position by trapping fluid under pressure in the hydraulic lines between the male half of the coupling and the implement. The trapped fluid enables safe positioning of the implement until its next use. Sunshine and/or ambient heating further raise the pressure in the hydraulic lines leading to the implement making it difficult to connect (couple) the male coupling half into the female coupling half of the manifold for continued operation of the implement. When an implement is uncoupled from the manifold, fluid is also trapped between the female half of the coupling and a shut off valve interposed between the manifold and the directional control valve. Sunshine and/or ambient heating tend to increase the pressure of hydraulic fluid in the hydraulic lines and in the coupling making it difficult to couple the halves of the coupling together.
In some applications, shut off valves are used to intentionally trap fluid between the shut off valve and the load when the load remains connected so as to maintain the safe positioning of the implement. The shutoff valves or their functional equivalent may be integral with the directional valve. In this instance too, sunshine and/or ambient heating tend to increase the pressure of hydraulic fluid in the hydraulic lines and in the coupling.
It is desirable to provide a coupling which makes disconnection of the coupling halves easier and reduces or eliminates spillage.
It is desirable to provide a coupling which enables the male half of the coupling to close prior to disconnection of the coupling so as to minimize spillage and so as to trap pressure in the male coupling half and the hydraulic line leading to the implement.
It is desirable that the coupling halves be capable of connection under pressure, that is, with pressure applied to both halves of the coupling. It is further desirable that pressure be reduced or eliminated in the female half of the coupling to facilitate coupling.
U.S. Pat. No. 5,937,899 to Zeiber discloses a female cartridge which is retained within a manifold. Axial and radial vent valves are disclosed. The '899 patent provides a male half of the coupling which pushes the inner body of the pressurized female half of the coupling (which includes a pressurized chamber between a piston and a relief valve positioning member) causing the positioning member to be displaced in a leftward or rearward direction which causes the venting of the female member. The male half of the coupling pulls the inner body of the female half of the coupling rightwardly or forwardly which causes the venting of the female member. The venting occurs when the male and female halves of the coupling are connected or disconnected.
U.S. Pat. No. 5,709,243 to Wells et al. discloses a low spill female coupling. A valve having an enlarged head is adapted to receive a male valve from the male half of the coupling such that the valves remain closed until respective parts thereof are brought into contact with each other so as to minimize spillage.
U.S. Pat. No. 6,095,190 to Wilcox et al. discloses a female coupling half having internal pressure relief. The female half has three valves: a main valve, a relief valve and a sliding sleeve valve. The relief valve is a ball and seats against an elastomeric seal mounted on the back side of the main valve. A push pin having flat edges operates the relief valve.
U.S. Pat. No. 4,077,433 to Maldavs illustrates a piston valve arrangement with a passageway through the valve to assist in assuring that the male ball valve remains open in high flow conditions from the male to the female. U.S. Pat. No. 4,881,573 to Durant illustrates a coupler having two poppet valves. The first poppet engages a ball check valve formed in the male coupling and the second poppet is actuated by a manually operated cam. A passageway exists in the piston to allow fluid to be vented or to pressurize the female valve.
U.S. Pat. No. 4,598,896 to Maldavs illustrates a coupler having a spool and a port within the spool. An annular seal is fixedly positioned about the port in the spool. The spool is slidable with respect to the seal which enables pressure to be relieved in the female during coupling and uncoupling with the male. U.S. Pat. No. 4,303,098 to Shindelar discloses a coupler having a female half which includes a female valve having an elongated stem for engaging the male half. The female half of the coupling is vented by a pivotable cam which moves the inner member of the female half to release its locking means and then opens a poppet valve to open the outlet port.
U.S. Pat. No. 4,249,572 to Shindelar et al. discloses a female half which is self-relieving. The female half includes dual poppet valves which are linked together. One of the poppet valves vents the female half of the coupling when the male and female valves are disengaged and uncoupled.
U.S. Pat. No. 5,730,185 to Wilkins et al. discloses a coupling wherein certain positions of the adaptor allow the venting of the dispenser half and the receptacle half. Venting is prohibited by the movement of seals relative to ports and passageways.
U.S. Pat. No. 3,730,221 to Vik provides an exterior vent valve.
U.S. Pat. No. 4,745,948 to Wilcox et al. discloses a coupling device which utilizes locking detents which lock a stem against the male valve which prevents reverse flow checking.